Here's one more sign of a thaw in U.S.-Iranian relations: A 2,700-year-old silver drinking cup, looted from a cave in Iran and seized by U.S. Customs officials a decade ago, was returned to Iran this week. Its value is estimated at a million dollars or more. The ceremonial drinking vessel from the 7th century B.C., cast in the shape of a winged griffin, has been sitting in a warehouse in New York for years. And for years, U.S. officials have been saying they couldn't return it to Iran until relations between Washington and Tehran were normalized. "This piece can't go back," the New York Post quoted James McAndrew, senior special agent in charge of cultural property for U.S. Immigration and Customs Enforcement, as saying in 2010. On Wednesday, the piece went back. "It is considered the premier griffin of antiquity, a gift of the Iranian people to the world, and the United States is pleased to return it to the people of Iran," the U.S. State Department said. The ancient vessel, known in art circles as a rhyton, has a history that's worthy of an Indiana Jones sequel: It's thought to be part of the Western Cave Treasure, a hoard of ancient silver that was found in a cave near the Iran-Iraq border in the late 1980s. Soon afterward, looters plundered the site — and some of those treasures found their way to the international antiquities market. Federal authorities say a New York art dealer named Hicham Aboutaam brought the Pre-Achaemenid artifact into the United States in 2000, and provided Customs officials with an invoice falsely claiming that the piece came from Syria. Aboutaam negotiated a deal to sell the artifact to a collector for $950,000 — but when federal agents caught wind of the sale, they seized the artifact and arrested Aboutaam on smuggling charges in 2003. In 2004, Aboutaam pleaded guilty to a misdemeanor charge in connection with the false import claim and paid a $5,000 fine. If the drinking cup was worth $950,000 a decade ago, it's worth at least a million dollars today. But it's probably worth even more as a diplomatic gesture: Iranian authorities have been seeking the rhyton's return for more than two decades. "The return of the artifact reflects the strong respect the United States has for cultural heritage property — in this case, cultural heritage property that was likely looted from Iran and is important to the patrimony of the Iranian people," the State Department said. "It also reflects the strong respect the United States has for the Iranian people."